1. Field of the Invention:
The present invention relates to an iris drive mechanism which is suitable for incorporation into a lens block.
2. Description of the Prior Art:
In an iris which enables exposure to be adjusted, two diaphragms are operated by a motor or so called ideal gyrator (IG) meter and the displacement of these diaphragms is substantially proportional to the rotational angle of a motor rotation.
Accordingly, even though the aperture is small and the rotational angle of the motor or IG meter (viz, the motor) is small, the diaphragms are displaced through the same distances as those when the aperture is large. This of course induces a considerable change in the F-number.
As a consequence, resolution of the F-number when the aperture is small is reduced and an automatic exposure (AE) control performance is accordingly deteriorated.